Tropical Plant Biology

Maass, Brigitte; Knox, Maggie; Venkatesha, S.; Angessa, Tefera; Ramme, Stefan; Pengelly, Bruce

2010 Tropical Plant Biology

doi: 10.1007/s12042-010-9046-1pmid: 20835399

In recent years, so-called ‘lost crops’ have been appraised in a number of reviews, among them Lablab purpureus in the context of African vegetable species. This crop cannot truly be considered ‘lost’ because worldwide more than 150 common names are applied to it. Based on a comprehensive literature review, this paper aims to put forward four theses, (i) Lablab is one of the most diverse domesticated legume species and has multiple uses. Although its largest agro-morphological diversity occurs in South Asia, its origin appears to be Africa. (ii) Crop improvement in South Asia is based on limited genetic diversity. (iii) The restricted research and development performed in Africa focuses either on improving forage or soil properties mostly through one popular cultivar, Rongai, while the available diversity of lablab in Africa might be under threat of genetic erosion. (iv) Lablab is better adapted to drought than common beans (Phaseolus vulgaris) or cowpea (Vigna unguiculata), both of which have been preferred to lablab in African agricultural production systems. Lablab might offer comparable opportunities for African agriculture in the view of global change. Its wide potential for adaptation throughout eastern and southern Africa is shown with a GIS (geographic information systems) approach.

Shedbalkar, Utkarsha; Adki, Vinayak; Jadhav, Jyoti; Bapat, Vishwas

2010 Tropical Plant Biology

doi: 10.1007/s12042-010-9055-0

The cactus family is unusual among tropical plants. Cacti, known for their minimum water requirement, have been grown extensively in arid lands, for food, feeds and medicinal and therapeutic uses.Several food products have cacti as a main ingredient. Cacti biochemical analysis substantiate the high nutritive value of this plant family. Tissue cultures, including micropropagation, callus, and cell suspension cultures have been established for numerous cacti species. Genetic engineering has opened opportunities for gene isolation and integration of genes from other sources for cacti improvement. Cacti might be a store house of stress tolerant genes for other crops. Since cacti can be cultivated easily with minimum agriculture inputs, they hold great potential for cultivation and farming on degraded lands and for at least partial remediation of degraded lands. The present review outlines some of the older and more recent research on the properties and applications for Opuntia and other cacti especially as they might apply towards agricultural sustainability.

Iyer, Suresh; Mattinson, D.; Fellman, John

2010 Tropical Plant Biology

doi: 10.1007/s12042-010-9052-3

Cassava (Manihot esculenta Crantz) roots, the fourth most important food crop of the world, is the major carbohydrate source for more than 600 million people in Africa, parts of Latin America, Oceania, and Asia. Besides being a rich source of starch (∼80% of root), the root is also rich in vitamin C, some carotenoids, calcium, and potassium. Upon harvest, roots begin a process of physiological decay within 24–36 h called postharvest physiological deterioration or PPD. The early events leading to PPD are not known. Research to date concerning the study of PPD has mostly focused on the signaling events several hours after harvest. Upon examination of physiological and biochemical changes occurring 3 or 4 h after cassava root detachment, changes in the nature and type of volatile compounds emitted, secondary metabolites accumulated, and changes in the expression of key genes in reactive oxygen species (ROS) turnover were observed along with a correspondent increase in tissue cytoplasmic singlet oxygen presence using radical-specific fluorescent imaging of tissue samples. It is likely that these findings have significant implications to help us understand and assist in dissection of the early events leading to the postharvest deterioration of cassava root.

Zhang, Wenli; Wai, Ching; Ming, Ray; Yu, Qingyi; Jiang, Jiming

2010 Tropical Plant Biology

doi: 10.1007/s12042-010-9053-2

A significant amount of genetic and genomic resources have been developed in papaya (Carica papaya, $$ {\hbox{2n = 2}} \times { = 18} $$ ), including genetic linkage maps consisting of nine major and three minor linkage groups. However, the 12 genetic linkage groups have not been integrated with the nine chromosomes of papaya. Bacterial artificial chromosome (BAC) clones associated with each linkage group were recently isolated. These linkage group-specific BACs were mapped to meiotic pachytene chromosomes of papaya using fluorescence in situ hybridization (FISH). The FISH mapping results integrated the 12 linkage groups into the nine papaya chromosomes. We developed a pachytene chromosome-based high resolution karyotype for the hermaphrodite plant genome of papaya cultivar SunUp. The chromosomal distribution of heterochromatin in the papaya genome is provided in the karyotype with the X chromosome representing the most euchromatic chromosome in the papaya genome. FISH mapping also revealed a significant amplification of sequences related to the 5S ribosomal RNA genes, which was detected in the male-specific region of the Y chromosome, but not in the corresponding region in the X chromosome.

Wai, Ching; Ming, Ray; Moore, Paul; Paull, Robert; Yu, Qingyi

2010 Tropical Plant Biology

doi: 10.1007/s12042-010-9054-1

Carica papaya L. is a tropical and sub-tropical fruit-tree crop with a small genome and nine pairs of chromosomes. The transgenic cultivar ‘SunUp’ has been sequenced and three high-density genetic maps are available for mapping agronomically and economically-important traits. However, the small size and similar morphology of papaya chromosomes hinder their identification and few cytological resources are available for integration of genetic and cytogenetic information. Fluorescence in situ hybridization (FISH) was performed on mitotic metaphase chromosomes using BAC clones harboring mapped simple sequence repeat (SSR) markers as probes. A total of 104 BAC clones covering all 12 linkage groups (LGs) were tested and 12 of them, that gave a single specific signal, were chosen as representative of the 12 LGs of the SSR genetic map. This set of chromosome-specific DNA markers acted as a foundation for papaya chromosome karyotyping and re-assigning orientation of LGs. Chromosome-specific markers allowed us to assign the minor LGs 10, 11, and 12 to major LGs 8, 9, and 7, respectively. We thus reduced the number of LGs in the genetic map to nine, corresponding to the haploid number of papaya chromosomes. We also tested the relative order of DNA markers on minor LGs 10 and 11 to place them on top of LGs 8 and 9 in the correct orientation. Ribosomal DNAs (rDNAs), a set of major cytogenetic markers, were positioned on specific papaya chromosomes. The 25S rDNA showed strong signals at the constriction site of a single pair of chromosomes identified as LG 2 by LG 2-specific BAC clone. The 5S rDNA showed strong signals on two pairs of chromosomes that are syntenic with LG 4- and LG 5-specific BAC clones. This integrated map will facilitate genome assembly, quantitative trait locus (QTL) mapping, and the study of cytological, physical and genetic distance relationships between papaya chromosomes.